A US aircraft carrier partaking in tripartite naval exercises with Japanese and Indian naval groups in the Western Pacific has been closely followed by a Chinese observation vessel.

The Wednesday incident took place as USS John C. Stennis was diverting the Chinese vessel away from the underway drills, codenamed Malabar.

The waters neighbor the South China Sea, which is claimed by Beijing almost in its entirety.

The US has increased its presence in the Asia-Pacific region through its so-called pivot strategy, which critics denounce as a provocative policy.

It has also been increasingly critical of China’s activities in the disputed islands claimed by Beijing in the South China Sea and, on occasions, dispatched aircraft and warships on patrols close to the territories.

Beijing, in turn, accuses Washington of meddling in regional issues and deliberately stirring up tensions in the South China Sea.

Last month, the Pentagon said two Chinese fighter jets flew within 50 feet (15 meters) of a US EP-3 aircraft over the South China Sea.

Japan has, meanwhile, joined forces with the US in alleging that China is pushing into the Western Pacific.

The current three-nation show of force, which also enlists a Japanese helicopter carrier and sub-hunting Japanese patrol planes as well as Indian frigates in seas off the Japanese Okinawan island chain, seeks to send a message to Beijing.

The South China Sea, which is believed to rest atop vast reserves of oil and gas, is also claimed in part by Taiwan, Brunei, Vietnam, Malaysia, and the Philippines.